Methods for measuring or estimating the load in a clothes washing machine are frequently found in the state of the art. These methods are of paramount importance as through the measurement of the clothes load it is possible to program the washing time and quantity of water used for the operations of a washing machine more precisely. Consequentially, it is also possible to save water and electrical energy, which has been a frequent and common concern with many technological developments, not just those which belong to the same field as the present invention.
Besides introducing advantages from an economic viewpoint, the methods of load measurement of the state of the art have been used together with control systems to automate operations of the washing machine, bringing practical advantages to the user.
As an example of the state of the art for a method of load measurement for washing machines, patent document U.S. Pat. No. 5,241,845 may be cited. This document describes a method which estimates the clothes load in washing machines from the measurement of the difference of phase angle between the engine current phase and the voltage supply phase of the same. Thus, this document sustains that the decrease of the difference of the phase angle is proportional to the potency of the engine. As such, considering that the engine potency is proportional to the volume of clothes to be washed, the changing of the phase angles is associated with the quantity of clothes in the basket of the washing machine.
Beyond this measurement characteristic, the method described in this US document uses other variables to automate the operation of the washing machine, such as: type of clothes, volume of detergent, type of detergent, transparency of the water and temperature of the water. There is at least one sensor and at least one circuit associated to each of these variables. As such, the method combines these variables through a neural network, to achieve the objective of controlling the washing operations of the washing machine.
As you can see, the method described in this patent U.S. Pat. No. 5,241,845 takes many variables beyond the clothes load into consideration to automate the operation of the washing machine. Although these other variables bring advantages to the consumer, the implementation cost of this method is high, considering the number of components necessary to measure and deal with the variables.
Another example of the state of the art is contained in patent document U.S. Pat. No. 6,038,724. This document describes a method which estimates the clothes load in a washing machine from variables of position and speed. More specifically, the method calculates the clothes load's moment of inertia based on the acceleration of the mobile assembly (in this case, stirrer) and the engine phase angle.
Throughout the text of document U.S. Pat. No. 6,038,724 it is stated that the method described requires a simple system of sensors and a controller for its viability. However, despite the method being able to be implemented through low cost components, it should be noted that the calculation of the moment of inertia presented by this document does not take into consideration that the load distribution within the mobile assembly influences the value which this quantity adopts. Besides this, the fact that other factors can influence the acceleration of the mobile assembly, such as, for example, the temperature of the engine, is also not taken into consideration. Therefore, the load estimate that does not take into account these characteristics of the moment of inertia is imprecise, and, therefore, needs to be improved in order to be employed successfully by those skilled in the art.
In this sense, it should be noted that the state of the art still does not include a method for the estimation of clothes load which is efficient and, at the same time, has low implementation cost.
Objectives of the Implementation
Therefore, providing a method to measure the clothes load in a washing machine which is efficient, reliable and robust while being low cost is an objective of the present invention.